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Applied and Environmental Microbiology, October 2004, p. 5929-5936, Vol. 70, No. 10
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.10.5929-5936.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Improved Stress Tolerance of GroESL-Overproducing Lactococcus lactis and Probiotic Lactobacillus paracasei NFBC 338

C. Desmond,1,2 G. F. Fitzgerald,2,3 C. Stanton,1,3 and R. P. Ross1,3*

Teagasc, Biotechnology Centre, Moorepark, Fermoy, County Cork,1 Department of Microbiology, University College,2 Alimentary Pharmabiotic Centre, Cork, Ireland3

Received 5 February 2004/ Accepted 20 June 2004

The bacterial heat shock response is characterized by the elevated expression of a number of chaperone complexes. Two-dimensional polyacrylamide gel electrophoresis revealed that GroEL expression in probiotic Lactobacillus paracasei NFBC 338 was increased under heat adaptation conditions (52°C for 15 min). Subsequently, the groESL operon of L. paracasei NFBC 338 was PCR amplified, and by using the nisin-inducible expression system, two plasmids, pGRO1 and pGRO2, were constructed on the basis of vectors pNZ8048 and pMSP3535, respectively. These vectors were transferred into Lactococcus lactis(pGRO1) and L. paracasei(pGRO2), and after induction with nisin, overexpressed GroEL represented 15 and 20% of the total cellular protein in each strain, respectively. Following heat shock treatment of lactococci (at 54°C) and lactobacilli (at 60°C), the heat-adapted cultures maintained the highest level of viability (5-log-unit increase, approximately) in each case, while it was found that the GroESL-overproducing strains performed only moderately better (1-log-unit increase) than the controls. On the other hand, the salt tolerance of both GroESL-overproducing strains (in 5 M NaCl) was similar to that of the parent cultures. Interestingly, both strains overproducing GroESL exhibited increased solvent tolerance, most notably, the ability to grow in the presence of butanol (0.5% [vol/vol]) for 5 h, while the viability of the parent strain declined. These results confirm the integral role of GroESL in solvent tolerance, and to a lesser extent, thermotolerance of lactic acid bacteria. Furthermore, this study demonstrates that technologically sensitive cultures, including certain probiotic lactobacilli, can potentially be manipulated to become more robust for survival under harsh conditions, such as food product development and gastrointestinal transit.


* Corresponding author. Mailing address: Teagasc, Biotechnology Centre, Moorepark, Fermoy, County Cork, Ireland. Phone: 353-25-42229. Fax: 353-25-42340. E-mail: pross{at}moorepark.teagasc.ie.


Applied and Environmental Microbiology, October 2004, p. 5929-5936, Vol. 70, No. 10
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.10.5929-5936.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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Copyright © 2004 by the American Society for Microbiology. All rights reserved.